Random blank/black X sessions with GDM on a Dell GX280 running CentOS 5

While upgrading a lab of Dell GX280 systems to CentOS 5 today I ran into a bit of a snag. Seemingly at random when the system initially started or returned to the GDM login screen the user would get a black screen. The system still responded on the network, could be switched to VTs and the GDM screen would correctly display after a few gdm-restart commands. I found this bug report but no solution. I did notice that when the screen was blank if the mouse was moved up, till it the cursor (were it visible) would hit the top of the screen, the GDM screen would pop up and function normally.